The present invention relates to a device for affecting the hydro dynamic system of the inner ear, which system includes the paralymph and endolymph. The device may be utilized for instance in the treatment of patients suffering from the Meniere's disease, as described in U.S. Pat. No. 4,757,807 which is included herein by reference.
A device of the type outlined above is described e.g. in WO 83/02556. This device comprises a first means for generating a desired static-pressure level, a second means for causing a variation of the static-pressure level, a third means for connecting said first and said second means to the auditory tube, and a fourth means for interconnecting the auditory tube and the middle ear to facilitate transfer of the pressure changes generated in the auditory tube to the middle ear to affect the hydrodynamic system of the ear.
The first means preferably is an air pump in the form of a diaphragm pump having a membrane that is affected by a reciprocating piston for build-up of the static pressure in a reservoir.
The second means includes a unit adapted to produce the movements of a membrane part which is connected to the reservoir, said movements designed to produce the variations of the static-pressure level.
In this device the movements of the membrane part of the second means are produced manually or by means of a second piston, which is connected to the membrane part and which by means of an eccenter device is arranged to be displaced by certain distance and in doing so displace the membrane part. It has proved to be important that the generated pressure pulses follow a certain predetermined configuration as closely as possible in order to provide maximum treatment results, it thus becoming possible to vary the configuration of the pressure pulses from one person to the next and from one treatment to the other. This prior-art device does not, however allow comparisons to be made between a generated pressure pulse and a desired pressure pulse, for which reason it is impossible to regulate the pumping effect in accordance with the configuration of the generated pressure pulses in order to obtain the desired pressure pulses. In order to adapt the configuration of the pressure pulses to a certain treatment or to a certain person some manual adjustment may, however, be effected. For instance, it is possible to replace the eccenter means. However, this is an inconvenient and time-consuming operation. Since the membrane part in accordance with one embodiment is displaced by a certain distance by an eccenter means, it is not either certain that the adequate pressure pulses are generated in the device, since it may be necessary to vary the distance, for example to compensate for certain leakage as may occur in the device or between the device and the ear.
It is medically proven that negative pressure (depression) in static form as well as in the form of infrasound are harmful to the ear. In the prior art device pumping movements may, at least initially, cause a negative pressure to be generated in the ear. This may happen for instance when a pumping movement starts by a suction stroke. Also, if for instance a valve means, such as non-return valve, is provided through which air is sucked into the device during the suction stroke, a certain depression may nonetheless be generated in the ear during the suction stroke.
WO 93/08775 discloses another device of the above-mentioned type. This device comprises a housing, a membrane disposed in the housing, and means for actuating the membrane. The membrane and the housing form a chamber which is connected to the ear by means of connection means. Pressure pulses are generated as the membrane is displaced by said means. The means includes a piston which is connected to the membrane. The piston is displaced by an electric motor. In order to create a static pressure the membrane is displaced by the piston by a predetermined distance in a first direction to a biased position around which the membrane is displaced to generate the pressure pulses. The device also includes a pressure-sending means adjacent to the connection means, which sensing means is connected to a control unit. When the static pressure is reduced, for instance on account of leaks at the ear, a signal generated by the pressure sensing mean is supplied to the control unit which in turn emits a signal to the membrane for displacement of the piston in the first direction to a new biased position, said displacement reducing the size of the chamber. A disadvantage inherent in this arrangement is that the dimensions of the chamber may become so small immediately or after several such displacements that the treatment must be interrupted to allow the chamber size to be increased once more by displacement of the membrane in the other, the opposite direction, whereupon a new static pressure must be built up. In addition, advanced control of the device is necessary in order to generate the desired pulses, with the result that the device has an expensive and complicated construction. Also in this device the pressure pulses are generated by displacement of the piston by a predetermined distance, which distance does not always produce the same pressure changes in the device, which is due, among other things, to the leakage variations between the device and the ear, resulting in unnecessary adjustments from the control unit that governs the piston displacements.
Also in the case of this device a pumping movement may, at least initially, produce a negative pressure in the ear, should the pumping movement start by a suction stroke, since a certain resistance against air through-flow always exist across the non-return valve that is connected to the chamber.
Generally speaking, the prior art solutions are deficient with respect to the control and the regulation of the pulses, leading to highly varying treatment results are in some cases negative ones. In addition, the prior art solutions produce a comparatively high level of noise, which the patient may find unpleasant and which in some cases may even be detrimental and thus negatively affect the treatment results.